Pneumatic system of and apparatus for handling railway-signals



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J. W. THOMAS, Jr. PNEUMATIG SYSTEM OF AND APPARATUS FOR HANDLING RAILWAYSIGNALS.

Patentedfiuneb, 1894.

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J. W. THOMAS, Jr. PNEUMATIC SYSTEM OF AND APPARATUS FOR HANDLING RAILWAYSIGNALS.

No. 520,813. Patented JuneL 1294.

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(Nd Model.)

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Patented June 5, 1894.

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5 SheetsSheet 5. J. W. THOMAS, Jr. PNEUMATIC SYSTEM OF AND APPARATUS FORHANDLING RAILWAY SIGNALS.

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JOHN W. THOMAS, JR., OF NASHVILLE, TENNESSEE.

SPECIFICATION forming part of Letters Patent No. 520,813, dated June 5,1894.

Application filed February 24, 1894. Serial No. 501,400. (No model.)

To all whom it may concern.-

Be it known that I, JOHN W. THOMAS, Jr., of Nashville, in theState ofTennessee, have invented a certain new and useful Pneumatic System ofand Apparatus for Handling Railway-Signals, of which the following is aspecification.

The fundamental feature of my invention resides in the fact that thevalve for admitting air to and exhausting it from the working cylinderof a signal is manipulated by means of a single controlling pipecontaining air at more than atmospheric pressure at all times-thepressure of this air being variable within defined limits and beingexerted upon a valve shifting piston which on the other side issubjected to continued air pressure, which also is variable with respectto the opposed pressure exerted by the air in the controlling pipethetwo pressures being equalized after the shifting of the piston in eitherdirection by means of one or more equalizing ports or passages leadingfrom one side of the piston to the other, through which air from theside on which preponderance of pressure for the time being existsgradually passes to the other side until the pressures are equalized.

Other features of the invention reside in the pneumatically operatedappliances for handling two position signals and three position signalsrespectively; in a device which may be termed a pneumatic selector,whereby one or the other of two signals is put in condition to beoperated according as the switch to which the same pertain, is eithernormal or reversed; and in other details which will be developed in thecourse of this specification.

I find that it is only by maintaining at all times more than atmosphericpressure in the controlling pipe, that the signal or signals can beworked efficiently and at the requisite speed. I prefer for this purposeto use compressed air in the controlling pipe between limits of sixtypounds to the square inch for maximum pressure, and fifty pounds to thesquare inch for minimum pressure; with this variation of pressure it isfeasible to handle the signal expeditiously and effectively. The

pressure in the main supply from which the air in the controlling pipeis drawn, I prefer to maintain at say eighty pounds to the square inch,for the reason that after pressure in the controlling pipe has beenreduced to the minimum of fifty pounds I find it much easier to restorethe pressure in that pipe to the maximum of sixty pounds when thepressure in the main is over that figure, than when it is the same asthe maximum in the controlling pipe. The reduction from eighty pounds inthe main to the maximum of sixty pounds in the controlling pipe iseffected by any suitable reducing valve interposed in the communicationbetween the controlling pipe and the main from which it draws itssupply. The reduction from the maximum of sixty pounds to the minimumof' fifty pounds in the controlling pipe is effected by providing theexhaust for the controlling pipe with a pop or relief valve of anysuitable construction, which is set or adjusted to open at pressuresabovefifty pounds.

By having a pressure in the main superior to the maximum in thecontrolling pipeIam also enabled to provide in a simple and efficientway for operating a three position signal.

To enable others skilled in the art to understand and use my invention,I will now proceed to describe the manner in which the same is or may becarried into effect by reference to the accompanying drawings, in whichFigure 1 is a side elevation, and Fig. 2 is a front elevation of theupper part of a signal mast carrying apparatus embodying my invention asapplied to a two position signal. Fig. 1 omits the valve which issho'wnin Fig. 2 for controlling the indicator in the. tower; and Fig. 2 omitsthe air reservoir which in Fig. l is in communication with the interiorof the valve chest. Fig. 2 is a vertical central section of theindicator controlling valve. in Fig. 2. Fig. 3 is a sectional sideelevation of the signal operating lever (supposed to be located in thetower) and its appurtenances. Figs. 4 and 5 are diagrammatic viewsshowing' each in plan and side elevation, the tappet connected to thelever and the indicator pin which works in conjunction with the tappet,in the different positions which they assume when the operating lever ismoved to set the signal from danger to safety. Figs. 6 and-7 arerespectively a front elevation and a side elevation of the upper portionof a signal mast provided with a three position signal and pneumaticallycontrolled appliances for operating the same. Fig. 8 is a verticalsection on enlarged scale of the appliances last mentioned. Fig. 9 is asectional side elevation of the signal lever and valve mechanism andpneumatic appliances for operating in connection with the three positionsignal. Fig. 10 is a diagrammatic view illustrative of a main line, andbranch or siding and a signal mast with two signals one for the sidingand one for the mainline. Fig. 11 is a longitudinal vertical section ofa pneumatic selector operated by the switch connecting the main line andsiding, and acting to determine which of the two signals shall beactuated according as the switch is normal or reversed.

In Figs. 1 and 2, A is an ordinary counterbalanced pivoted semaphoreblade, which normally is held at danger bya pivoted counter weightedlever 3, joined to the shorter arm of the blade by a connecting red asusual. Lever 3 at its shorter end is jointed by a connecting rod to apiston 2 which can move up and down in the working cylinder 1, into thetop of which, at a point above the piston, leads the central port 11,from a valve chest 5. This port 11 is located between two ports 9, 10,in the same el1est-all of these ports be ing formed in a valve seat uponwhich plays the slide valve D, by which the central port 11 is thrownalternately into communication with port 10 and port 9. Port 10 is thesupply port and through itcompressed air, taken from the main supplythrough a suitable communication, is supplied to the working cylinder 1for the purpose of forcing down piston 2 against the resistance of thecounterweight 3 and thus bringing the signal from danger down to safety.Port 9 is the exhaust port and through it air is exhausted from theworking cylinder with the effect of allowing the counterweighted lever 3to raise the signal to danger--this being the normal position of thesignal.

The slide valve D is held between collars on a stem, which is fast tothe piston 8 seated and adapted to move back and forth in the case 5. Inthe head of this case opposite the outer face of the piston is a pipe6-hereinbefore referred to as the controlling pipewhich contains at alltimes air at more than atmospheric pressure. Under the conditionspreferred by me, the maximum pressure in the pipe should be sixty poundsto the square inch and the minimum pressure should be fifty pounds tothe square inch.

The piston--which I term an equalizing pistonhas in it an equalizingport or passage 7, through which air can feed gradually from one side ofthe piston to the other. In the position of parts shown in Fig. 1,pressure in the controlling pipe is supposed to be reduced to fiftypounds; and by means of the equalizing port 7 air has passedthrough tothe opposite side of the piston so as to make the pressure from thatside also fifty pounds.

Now if the pressure in the controlling pipe be suddenly raised (theappliances for this purpose will be presently described) to say sixtypounds then as this increased pressure on the controlling pipe side ofthe piston, takes place more rapidly than it can feed through to theother side of the piston, it will have the effect of forcing the valveover to the right, thus shutting the working cylinder off from theexhaust 10 and putting it in communication with the supply 9. After thevalve has shifted, the gradual feed of air through the port- 7 willequalize the pressures and the valve will again be balanced; so thatwhen pressure is suddenly reduced on the side of pipe (3 to fifty poundsthe valve by the stored pressure on the other side of the piston, willbe thrown over to the left to reassume the position shown in Fig. 1. Forthe purpose of giving increased capacity to the chest or case 5 on theside of the equalizing piston opposite to the controlling pipe and thusproviding for increased compressed air storage on that side-I connect tothe latter an auxiliary reservoir or case 4 (Fi 1). The foregoing willsuffice to explain the operation of the equalizing piston.

I proceed now to adescription of the means for varying the air pressurein the controlling pipe for the purpose of handling the signal. Thesemeans are shown in Fig. 3.

The parts about to be described are mounted on or secured to a suitabletable or frame 12 in the tower. The signal operating lever is designated14. It is capable of assuming successively the positions marked A. B. O.and is provided as customary in this class of appliances with a springlatch to engage a notched quadrant. The lever, as also is customary issuitably jointed to a sliding tappet 13 mounted on the table andintended forinterlocking purposes, by which all conflicting lovers arelocked up at the proper time. The signal lever 14 is an elbow lever andits shorter arm is by a connecting rod linked to a valve stem 15,adapted to reciprocate in the valve case or chest 16. This stem actuatesthe slide valve D which is held between collars on the stem and playsback and forth over ports 17,18, formed in a seat on the chest. Openinginto the chest a pipe 10 communicating with the main air supplythiscommunication being provided with a suitable reducing valve by which theeighty pounds pressure in the main is reduced to say sixty pounds. Theport 17 com m unieates with the controlling pipe (5 in Fig. 1; the port18 is the exhaust port, to be armed with a pop or relief valve set tofifty pounds pressure.

In Fig. 3 the valve D bridges the ports 17, 18-which is the position itoccupies when the parts shown in Fig. 1 are in the position representedin that figure. W hen the operating lever 14 (Fig. 3) moves from A to Oposition, the valve D will thereby be shifted to uncover the port 17thereby putting the latter in communication with the supply 19, and

consequently raising the pressure in the controlling pipe 6 from fiftyto sixty pounds. In this movement of the lever 14 it is desirable,before the valve D is shifted, that all conflicting levers should belocked. This result is obtained by permitting a certain movement to thelever at the outset, independent of the valve D, to which end (as shownin Fig. 3) I place the collars on the stem 15 farther apart than thelength of the slide valve D which lies between them, thus permitting thelever 14 independent movement at the outset before the valve will bemoved. The tappet 13 partakes of this initial movement of the lever andin so moving locks (by interlocking mechanism not necessary here todescribe) all conflicting tappets and consequently all conflictinglevers. The movement of the lever from A to 0, will have the effect ofsetting the signal to safety. On'the other hand the movement back from Gto A will have the effect, by reducing the pressure in the controllingpipe, of restoring the sig nal from safety to danger-the unlocking ofconflicting tappets taking place only during the concluding part ofthisreturn movement of the tappet attached to the lever. It is importantthat, in this return movement, it should be impossible for the operatinglever to move far enough to cause its tappet to unlock conflictinglevers or to do any mechanical locking unless its signal has certainlyreturned to danger. That signal for example might stick at safety, andin that event if the lever were free to return far enough for its tappetto unlock conflicting levers, conflictin g signals might be given. Toguard against any such contingency I provide a pneumatically actuatedindicator connected to and controlled in its action by the signal, andoperating as a stop or detent to arrest the lever before the completionof its return movement, unless the signal has actually gone from safetyto danger. This device with its connections is shown in Figs. 2, 2 and3. 'It consists of an indicator pin 20 attached to and projecting fromthe top of a rectangular oblong frame 21, (shown detached and in frontelevation on the left of Fig. 3,) which embraces and can move up anddown in guides on the cylinder 24 attached to the lever and tappetcarrying frame in'Fig. 3 and arranged beneath the tappet 13 to bring thepin 20 in when thus depressed will act to lower the pin 20 out of thepath of the .tappet. The pipe 26 leads to and communicates wlth a portin a valve chest or case 27 (Figs. 2 and 2 on the signal mast. Thischest also has an exhaust port 29, which if desired may be controlled byapop or relief valve set to open at a pressure so low as to be overcomeby the force of the spring 25 (Fig. 3). These ports are controlled by aslide valve D provided with a stem (1 which is linked to the semaphoresignal, the adjustment being such that when the semaphore stands atdanger the valve D will uncover the port 26. Into the chest 27 leads apipe 28 communicating with a source of compressed air supply havingsufficient pressure or head to overcome the resistance of spring 25(Fig. 3). Consequently when the parts are in the position shown in Figs.2, 2 and 3, the port 26 will be open, compressed air will be admittedtothe indicator cylinder 24 over the piston and the indicator pin 20will be held down out of the path of the tappet. The position in whichthe pin 20 stands in relation to the tappet at this time is indicated inFig. 4the depressed pin being beyond the right of slot .9 and under thesolid part of the tappet.

In moving the operating lever from Ato 0 position, the moment thesemaphore blade leaves its danger position, pipe 26 will by theconsequent movement of valve D be put in communication with exhaust port29; this will reduce the air pressure above the piston in the indicatorcylinder and the pin 20 will therefore be forced up to engage the slot 8which by this time has been brought over the pin. The operating levercan then be carried to its 0 positionthe pin 20 atthe conclusion of themovement of the tappet being at the left hand end of the slot 8. Uponthe return movement the signal should go to danger by the time the leverpasses from its 0 to its B position, atthe conclusion of which movementthe elevated pin will engage the right hand end of the slot 8 in thetappet as seen in Fig. 5. If the signal responds properly and actuallygoes to danger, then the valve D will shift so as to open the indicatorpipe 26 to the compressed air supply, the pin 20-consequently will bedrawn down out of engagement, and the lever will be free to accomplishthe concluding portion of its movement from B to A-in the course ofwhich, as hereinbefore stated, the tappet unlocks all conflictingtappets. of responding properly should stick at safety then the valve Dwould not beshifted, pressure in the indicator pipe 26 would not berestored and consequently the pin 20 would remain up in engagement withthe tappet thus locking the lever from further movement toward its Aposition, and preventing that movement of the tappet requisite to unlocksay a signal which has only danger and safety positions. When however itis required to handle a three position signal-or But if the signalinstead IIO one which has between its two extreme positions of safetyand danger a third and intermediate position indicative of caution -theapparatus shown in Figs. 6, 7 and 8 can efficiently be used. I use asbefore an equalizing piston for controlling the valve mechanism; butinstead of one working cylinder I have two, the one for caution and theother for safety, I employ two air controlling valves one for thecaution and the other for the safety cylinder, the one being arranged towork at a lower pressure than the other; and I provide for obtainingthese varying pressures in the controlling pipe by the movement of thesignal operating lever, which is connected to and operates what may betermed a three position valve-a valve which in one position opens thecontrolling pipe to the exhaust or minimum pressure outlet, in anotherposition opens that pipe to a pressure inlet, supplying air at apressure (say sixty pounds) sufficient to operate the caution valve, andin still another position opens that pipe to an inlet supplying air atincreased pressure (say eighty pounds) sufiicient to operate the safetyvalve. The details of the apparatus by which this result is attained areillustrated in Figs. 0, 7, 8 and 9.

The counterbalanced semaphore blade is pivoted on the signal mast, andis joined by a connecting rod to a pivoted counterweighted lever, as inthe apparatus hereinbefore described. The other end of thiscounterweighted lever is jointed to a rod (1 which at the other end isjointed toa piston 1) working 1 in a cylinder 0. This cylinder is thesafety cylinder; the permitted throw of its piston is sufficient tocarry the signal from danger to safety. Adjoining the safety cylinder isa second but shorter cylinder cthe cantion cylindercontaining a piston bwhich has pinned to it a rod a that at the other end is formed toencircle and slide on the rod a-this rod on when the signal is in normalor danger position abutting at its lower end against a shoulder a on reda. The downward movement of the rod a is limited by an internal stop orshoulder a with which the cylinder 0' is provided. The downward movementof rod 0, will by the bearing of that red upon the shoulder a of themain red a pull down the semaphore blade, and the stop a is so arrangedas to arrest this movement when the blade has reached the cautionposition represented in Fig.6. Thus the force applied from above to thecaution piston I) alone will suffice to bring the signal from danger tocaution; to move it farther from caution to safety the rod a is nolonger available, but by applying force from above to the safety pistonb, the signal can readily be still further lowered to safety, the rod asliding freely through the end of the rod (1. by which it is looselyencircled. Thus by applying a force, such as compressed air, from abovethe pistons 11,1), successively, the signal can he moved successivelyfrom danger to caution and from caution to safety, or by moving thesignal operating lever its full stroke so as to supply the safetycylinder immediately with compressed air the signal can move at oncefrom danger to safety without any intermediate stop. For the purpose ofregulating the supply and exhaust of compressed air needed for thispurpose, I provide in the head which closes the upper ends of the twocylinders two sets of ports 6, f, g, one for each cylinder-e in eachcase being the inlet to the cylinder, f, the port through which air issupplied from the main, and g the exhaust port opening to theatmosphere. These two sets of ports are in a seat on which are placedtwo slide valves D D one for each set of ports. These two slide valveshave a stem (Z to which they are held by collars or flanges, thedistance between the collars (1., (1 between which the safety valve D isincluded, beingsufficiently greater than thelength of that valve, topermit the stem a movement to the right sufficient to shift the valve Dbefore the valve D is moved. This is illustrated in Fig. 8, in which theparts are shown as they stand when the signal is at danger. In shiftingthe valves so as to supply compressed air to the cylinders, it will benoted that the stem will move far enough to shift valve D before collardmeets valve D, further movement of the stem in the same direction afterthat, will of course have the effect of shifting valve D also. The stemis connected to an equalizing piston h having an equalizing port 72.,similar to the equalizing piston already described and combined in likemanner with a chest 7L2 and storage chamber or reservoir h. Intothe headof the chest opens the controlling pipe t' containing at all times airabove atmospheric pressure but having that pressurevaried at propertimes by mechanism located in the tower and controlled by the signaloperating lever. Within the chest 71?, and beyond but in axial alignmentwith the valve stem cl, is a spring pressed rodj which at the endcontiguous to the stem enters the bearing in which the stem at that endslides, and is prevented from entering that hearing to more than apredetermined extent by a collarj with which it is provided. In thenormal position of the parts represented in Fig. 8 the adjoining ends ofthe valve stoned and the rodj are separated from each other by aninterval sufficient to permit the stem to move far enough to shift thecaution valve D far enough to the right to open the air supply to itscylinder, before said stem abuts or brings up against the rod j. Iftherefore only sufficient force be applied to the stem to shift thevalve D this force manifestly will not suffice to still further move thestem against the added resistance of the spring pressed rod j thedistance needed to shift the valve D" also. Consequently if the airpress ure needed to shift the caution valve to the right be sixty poundsthen that pressure might be increased say to eighty pounds in order toshift the safety valve D Pro- VlSlOll for this, is made by the apparatusrepresented in Fig. 9, which, as far as it goes resembles that shown inFig. 3, save that the slide valve is a three position valve opening thecontrolling pipe not only to the exhaust and the usual sixty poundspressure inlet as in the figure last named, but also to a further andhigher pressure inlet-supplying a pressure of say eighty pounds.

In Fig. 9 the operating lever, table and tappet are the same as in Fig.3; and the lever 1n like manner is linked to the slide valve. The valve(marked has however, in addition to its D cavity, an opening it beyondthat cavity, which is intended at stated periods to open communicationbetween the port 10 and the interior of the valve chest. The chest isalso provided with three other ports, Z, Z, and m. Z communicating withthe controlling pipe '11, Z being the exhaust closed by a pop or reliefvalve set to close at any predetermined minimum pressure-say fiftypounds-and the remaining port m belng in communication with the mainsupply through a pipe or communication at which delivers the air at thefull head of eighty pounds. A branch pipe 0 from the supply enters thevalve chest, but this pipe is provided with a reducing valve whichreduces the pressure of air entering the chest to sixty pounds.

In the, position of parts shown in Fig. 9 both supply ports are closedand the controlling pipe is open to the exhaust as it should be when thesignal actuating mechanism is in the position shown in Fig. 8 with thesignal at danger. Air stands at the minimum'pressure of fifty pounds inthe controlling pipe. It now the operating lever be moved from A to Bposition, the valve 70 will be shifted to bring its opening lo" over thesupply port 10 thus closing the exhaust and admitting air at sixtypounds pressure from the valve chest into controlling pipe 1, with theresult of moving the equalizing piston far enough to shift the cautionvalve D and thus bringing the signal from danger to cautionthe valvestem 61 at this time abutting against the spring pressed rod j. If nowthe valve it be still further moved by throwing the lever from B to 0position, the port 10 will be closed while the valve will bridge theports Z and m, thus in creas1n g the pressurein the controlling pipe toeighty pounds. By this increase of pressure, the spring pressed rod isforced to the right. As. the pressures on both sides of the equalizingpiston approach equality, the now superlor power of the spring willassert itself and the rod j will be returned to its original position.In so doing it will also move the valve stem 01 correspondingly, but atthe conclusion of the movement of the stem (1 to the right the collar dwas separated from the adoining end of the valve D by a distance equalto the return movement of the rod j, so that the latter in. returningwill have moved the valve stem only the distancerequired to bring thecollar d up against valve D and consequently the latter will remainundisturbed, until the after reduction of pressure in the controllingpipe-upon which both valves will return to their original position.

Where the switch of a junction or siding is handled from the tower, itis customary to guard that point by a signal mast carrying two bladesthetop blade for the main line and the bottom blade for the siding. Theseblades are usually handled by one lever, through the agency of aselector, connected to and actuated by the switch, and acting todetermine which blade shall be lowered when the signal lever in thetower is reversed. To meet this requirement in my system I have devisedwhat may be termed a pneumatic selector, the construction and mode ofoperation of which can best be explained and understood by reference toFigs. 10 and 11.

Fig. 10 is a diagrammatic representation of the switch between the mainline and siding, together with a signal mast having two blades thereon.Each of these blades will have its own independent equalizing piston andappliances connected therewith such as represented in Fig. 1. In otherwords the apparatus shown in Fig. 1 will be duplicated. Instead,however, of the supply or controlling pipe 6 (Fig. 1) leading directlyfrom the signal valve in the tower to the equalizing cylder (or eitherof them on the mast) that pipe leads from the signal valve to thecentral port 10 of the group .of ports 10, p, 19 at the right hand endof the valve chest F, Fig. 11, over which plays a slide valve D heldbetween collars on a valve stem r the ends of which project out throughthe opposite ends of the valve chest in position to be operated on byknockers s on a reciprocatory rod Gattached to the stem of the piston ofthe working cylinder for actuating the switch. The rod G slides back andforth beneath the valve case or chest F and is connected to appliances,which need not be shown, for throwing the switch. At or near theconclusion of its movement in either direction, and after the switch hasbeen fully thrown, one or the other of the knockers s strikes and movesthe valve stem with the effect of shifting valve D. To the left of valveD and the group of ports controlled by it, are two other groups of portsand valves for controlling the same. These parts, which are notdistinguished by any reference letters or numerals, form part of apneumatic switch operating apparatus, and require no description here.They will be found fully described and illustrated in my application ofeven date herewith for Letters Patent for a pneumatic system of andapparatusfor handling railway switches. It will suffice for presentpurposes to say that the interior of the chest is supplied constantlywith compressed air drawn from a suitable source, so as tocounterbalance the valves.

As above said, the pipe 6 from the signal valve in the tower (Fig. 3)should in this arrangement lead to the central port 1). Port 1)communicates with the controlling pipe of the equalizing pistonarrangement of one of the two blades on the mast in Fig. 10 (in thisinstance the top blade) and port 11 in like manner communicates with thecontrolling pipe of the equalizing piston arrangement of the other ofthe two blades. It will thus be seen that by shifting valve D to one orthe other of its two positions the controlling pipe of either one or theother of the equalizing cylinders on the mast will be thrown intoconnection with the pipe 6 of the signal valve in the tower; and as thisshifting of the valve D is due to the movement of the switch, itfollows-that one or the other of the signal blades on the mast can beoperated according as the switch is normal or reversed. In Figs. 10, and11, the switch is supposed to be in normal position (for main track) andunder these conditions the selector valve D will stand as shown in Fig.11, bringing the signal valve in the tower in communication (throughport 1)) with the controlling pipe for the top blade, which now can belowered to safety whenever desired. On the other hand, with switch inreversed position the valve D will have thereby been shifted to the leftso as to open communication between the signal valve in the tower andthe port p leading to the controlling pipe of the second or bottomblade. In this way I provide a pneumatic selector by which theappropriate one of two signals can expeditiously and with certainty bebrought into communication with the one signal valve in the tower.

It will of course be understood that the pneumatic selector justdescribed can in a similar way be interposed between the signal valveand the equalizing piston mechanisms of the three position signal systemillustrated in Figs. 6 t0 9 inclusive.

In lieu of making an equalizing passage through the piston, manifestlyit can be formed in that portion of the walls of the cylinder traversedby the piston.

I remark also that in lieu of using the spring in the indicator cylinderto act on the indi cator piston, I may use compressed air, a weight, orany other suitable appliance for the purpose.

Having described my invention and the best way 110w known to me ofcarrying the same into eifect, what I claim herein as new, and desire tosecure by Letters Patent, is as follows:

1. In combination, a controlling pipe contmunicating with a source ofcompressed air supply, means for reducing and restoring air pressure insaid pipe; an equalizing piston and cylinderthe latter connected to saidpipe; a working cylinder and piston and a signal connected thereto so asto be operated by the movement of the piston; and a valve mechanismcontrolled by the cqualizing piston for admitting compressed air to andexhausting it from the working cylinder, the combination being andacting substantially as hereinbefore set forth.

2. The signal operating lever, its tappet and the pneumatic indicatormechanism, in combination with the signal, and valvemechanism foradmitting air to and exhausting it from the indicator cylinder,connected to and operated by the signal at the times and in the mannersubstantially as hercinbefore set forth.

3. The pneumatic selector, comprising a valve connected to and operatedby the switch or some part moving therewith, and three ports controlledby said valve communicating, one with the supply port of the signalvalve in the tower, and the other two with controlling pipes leading tothe cylinders of two valve shifting piston mechanisms, for operatingeach in connection with a distinct and separate signal, under thearrangement and for operation substantially as hercinbeforc set forth.

4. The mechanism for operating a three position signal comprising athree position signal valve in the tower adapted to deliver and graduateair pressures; a single controlling pipe through which said pressuresare delivered; an equalizing piston and cylinder-4110 latter connectedto the controlling pipe; two working cylinders, one for caution" and theother for safety; working pistons one for each cylinder whereby thesignal may through suitable intermediaries be actuated; a setotadmission and exhaust ports for each cylinder; two valves connected toand operated by the equalizing piston in such manner that the cautionvalve will move far enough to open its cylinder to the admission ofcompressed air, before the safety valve is moved to admit air into itscylinder; and a graduated spring or yielding resistance which opposessuch movement of the safety valvc-the combination being and actingsubstantially as hereinbefore set forth.

In testimony whereof I have hereunto set my hand, before two subscribingwitnesses, this 10th day of February, 1894.

JOHN V. THOMAS, JR.

Witnesses:

EWELL A. DICK, Roar. W. Cox.

